Yes, you should worry about patent infringement. But that doesn’t necessarily mean that you are infringing just by reselling. I would suggest speaking with a patent attorney to determine whether your specific activity is infringing a patent.
Generally, a patent will protect its holder from others attempting to sell the same or similar goods. However, patents are limited to a specific region, so if the goods in question are only patented in China, there would be no problem reselling them in the US assuming you acquired them legally. Many other factors are in play though so you should really speak with an attorney about your situation to determine the legality of your conduct.
To answer your other questions, you generally would only be sued for any damages caused by your reselling. That means that you would not be sued in excess of what you make, but you would probably have to give up all of your profits.
Again, the act of reselling is not itself illegal — there are ways to resell patented goods legally. One very common way is to acquire a license from the patent holder. This would cost you some profits, but would be a very easy way to stay out of trouble.
I hope this answered your question, but if you are looking for a patent attorney, you should visit. Many inventors turn to us in order to connect with top attorneys across the country. We offer start to finish project management, free initial consults, flexible payment options and a satisfaction guarantee. Hope this helps!